The invention relates to a vehicle brake system having a gas pressure accumulator, which comprises a housing, the interior of which is divided by metal bellows and a disk fastened to the metal bellows in gas-tight manner into a gas-filled gas chamber and a fluid chamber, wherein via a feed line a fluid may be supplied under pressure to and removed from the fluid chamber, and provided between the fluid chamber and the feed line is a valve arrangement which closes when the pressure in the feed line drops below a minimum value and opens when the pressure exceeds the minimum value, wherein the metal bellows during supply and removal of the fluid executes a stroke motion by means of which the valve arrangement is actuated. The invention further relates to such a gas pressure accumulator.
During operation of the vehicle brake system, the fluid chamber of such gas pressure accumulators is filled, counter to the pressure in the gas chamber, partially or completely with brake fluid, in order to store the latter.
Particularly high standards are demanded of vehicle brake systems with regard to the operability and reliability of the equipment.
An object of the invention is therefore to provide a safe and reliable vehicle brake system.
An object of the invention is achieved according to the invention by a vehicle brake system of the type described initially having a gas pressure accumulator which comprises the features of claim 1. An object is further achieved by such a gas pressure accumulator. Since the metal bellows executes a stroke motion during supply and removal of the fluid by means of which the valve arrangement is actuated, the closing of the fluid compartment is directly responsive to the movement of the metal bellows whereby a closed safety system is formed.
Further developments of the invention are the subject matters of the dependent claims.
Advantageously connected to the hollow cylinder is a coaxial mandrel on which the piston is guided or which is guided in the piston. By said means a guided movement of the piston relative to the sealing seats is possible and, at the same time, a compact structural shape of the gas pressure accumulator is achieved.
According to a development, the metal bellows are substantially in the shape of a hollow cylinder and the piston as well as the hollow cylinder are disposed radially inside the metal bellows, with the result that a particularly compact structural shape is achieved.
An advantageous refinement provides that the stroke motion of the metal bellows is delimited by two end stops in order to preset defined end positions for the movable components. In the end positions is the valve arrangement in each case closed at the same time.
A seal or a sealing seat is advantageously formed on at least one end stop. On the end stop, therefore, a redundant seal is formed which enables particularly good sealing. In a particularly advantageous manner the redundant seal is disposed on the end stop delimiting the normal position of the piston. Thus, the gas pressure accumulator is sealed particularly well when the pressure in the feed line is lower than the admissible minimum pressure. The pressure in the feed line, the so-called system pressure of the vehicle brake system, may drop below said minimum pressure, the so-called gas admission pressure, especially during extended stationary periods of the vehicle.
The gas pressure accumulator may alternatively be provided with a valve arrangement, which is provided with at least one redundant seal on an end stop but does not have the dual function described above. Given such a valve arrangement, the piston as closing element during a closing motion first contacts a first sealing seat and effects sealing there. Then the piston contacts a second sealing seat, which forms an end stop for the closing element, and effects redundant sealing there. The first sealing seat may correspond to one of the sealing surfaces described above.
To ascertain the necessary tightness of the valve arrangement, at least one seal is advantageously disposed on the piston which may effect sealing against at least one sealing seat.